1. Field of the Invention
This invention relates to an improved helical gear differential including lubrication passage means for supplying lubricating oil from the differential casing to the ends of the helical pinion gears and the side gears, thereby to increase the operating life and durability of the differential. An improved cross pin spacer arrangement is provided that affords easy, quick and inexpensive assembly of the differential on a vehicle production line.
2. Brief Description of the Prior Art
Helical gear differentials are well known in the patented prior art, as evidenced by the patents to Myers U.S. Pat No. 3,706,239, Dissett U.S. Pat Nos. 4,625,585, 4,677,876, and 4,751,853, Dissett et al U.S. Pat No. 4,365,524, and Bawks et al U.S. Pat No. 5,221,238. These differentials include pairs of longitudinally offset helical pinions that are mounted with an outside diameter running fit in the pinion cavities and which are in enmeshing engagement at their adjacent ends, the remote ends of the pinions being in enmeshing engagement with the side gears, respectively. The transverse forces caused by the gear tooth loadings on the pinions cause an inherent frictional resistance at the outside diameter fit, thus introducing an inherent torque bias that is proportional to the transverse gear tooth loading, which in turn is proportional to the torque transmitted through the differential assembly. The helix angle of the gears introduces an axial thrust on the respective differential pinions causing a frictional drag owing to the frictional engagement of the axial ends of the pinions with the bottom wall surfaces of the pinion cavities of the differential carrier housing.
The friction produced by the reaction forces on the housing at the axial ends of the meshing pinions is created by the thrust forces of the helix angle of the gears. These friction forces on the housing complement the friction forces created by reason of the sliding contact of the addendum surfaces of the pinions on the circular walls of the pinion cavities. The friction forces can be varied by altering the diameter of the pinions, their circular pitch, or their helix angles, thereby providing parameters that can be varied to suit several particular design requirements. Also, the number of pairs of pinions may be increased, if desired, to add to the torque capacity of the differential. The thrust forces produced at the ends of the helical pinions and the side gears tend to stress and produce wear on the adjacent housing support surfaces, thereby adversely affecting the operation of the differential, and reducing its operating life. Furthermore, the housings of the known helical gear type differentials are relatively bulky and heavy, thereby increasing the cost of the differential and the installation thereof. Also, the known helical gear differentials have a relatively high noise level in operation.
It is conventional in such helical gear differentials to provide cross pin spacer means than extend transversely between the ends of the output shafts or axles that are driven by the differential, thereby to prevent axial displacement of the shafts toward each other. These cross pin spacer means are installed after the C-clip retainers are connected with the output shafts to prevent axial separation of the shafts relative to the differential. The known cross pin spacer means are generally of rather complicated construction, and are difficult and expensive to install.
The present invention was developed to avoid the above and other drawbacks of the known types of helical gear differentials.